The present present invention relates to a hydraulic power steering system for automotive vehicles including a power cylinder coupled to a mechanical steering assembly, a pump and a control valve.
A hydraulic power steering system of this type is known from published German patent application No. 28 39 121. This known power steering system is comprised of a measured variable transmitter depending on the angle of rotation. The transmitter serves as a sensor for the hand power applied to the steering wheel. The output signal is transmitted to an electronic control module which controls the solenoid valves which are located between the pump and the power cylinder. In addition to their sophisticated and cost-intensive arrangements, these known power steering systems have the disadvantage that the steering assembly may become locked in the event of a defect of the electronic control module. Although this risk could be avoided by the redundant design of the electronic control system, the resulting increased sophistication would nevertheless result in a further disadvantage.
It is, therefore, an object of the present invention to provide a hydraulic power steering system for automotive vehicles of the type described above which is distinguished by a simple arrangement and which ensures safety in operation. In particular, the hydraulic power assistance dependent on demand is controlled without sophisticated electronic modules.